In upstream oil and gas operations, hydrocarbon liquids and gases are typically produced with some contaminants, such as acid gases and sulphur compounds. Acid gases are gases which form acidic solutions when mixed with water, and typically include hydrogen sulphide and carbon dioxide. Hydrogen sulphide is a colorless, flammable, poisonous gas, having a characteristic foul odor of rotten eggs. It may be produced from the bacterial breakdown of organic proteinaceous matter from plants or animals, or by contact at high temperatures between elemental sulphur or certain sulphur-containing compounds and organic materials. Hydrogen sulphide may also be formed as an undesirable byproduct in various industrial processes such as, for example, the production of coke from sulphur-containing coal; the refining of sulphur-containing crude oils; the production of disulphide; the manufacture of viscose rayon; and the Kraft process for conversion of wood into wood pulp.
Hydrogen sulphide may also be a byproduct of wastewater from treatment plants or water from agricultural practices. Unpleasant odors from liquids used in janitorial processes, RV holding tanks, portable toilets and the like are typically attributed to hydrogen sulphide. Such foul odors may be eliminated if the emission of hydrogen sulphide could be controlled in some manner.
Natural gas or crude oil having high concentrations of hydrogen sulphide are known as “sour gas” and “sour crude” respectively. Hydrogen sulphide in sour gas and crude oil streams is separated during gas sweetening processes, such as the widely used amine process which requires a solution of water and an amine to remove carbon dioxide and several sulphur compounds.
Since hydrogen sulphide is toxic, it represents a significant threat to public safety and health, and has potential to cause serious health risks in the oil and gas, livestock, waste management, and janitorial industries. At 200 ppm, hydrogen sulphide is undetectable by smell, and a concentration greater than 200 ppm induces nausea and headaches. At 500 to 1000 ppm, hydrogen sulphide leads to unconsciousness, with death resulting within two to twenty minutes unless the victim is removed immediately from exposure.
Other contaminants of natural gas or crude oil include sulphur compounds such as mercaptans.
It may be desirable to control bacteria which are known to produce hydrogen sulphide and other undesirable sulphur compounds.